The present invention relates to the field of dressings, and more particularly to the field of dressings for wounds, surgical cuts and other lesions to the human skin with anti-microbial properties.
Silver and other metals have been long recognized as being effective disinfecting agents. Compounds having a metal component that cause a metal ion exchange in the presence of a solution have been shown to destroy and inhibit the growth of many types of microbes, such as bacteria, fungus and other organisms. Silver nitrate is one well-known compound that is used as a disinfectant, but only in limited circumstances because it is primarily available in solution form. Silver is also used in pharmaceutical compositions, such as silver sulphadiazine, in the form of an ointment for topical application. Such applications complicate the wound treatment process by requiring a step to apply the anti-microbial agent, and a step to add the dressing.
It would be desirable to provide wound-dressing devices with metal-based disinfecting agents to provide the devices with a disinfecting function without additional steps in the wound treatment. Some known dressings use silver and other metals as disinfecting agents either in their sold metal state, or in the form of soluble compounds, such as soluble salts of acetate or nitrate. When applied to an exudating wound, silver ions are released into the wound as the molecules are dissolved. Such solutions tend to be inefficient, however, since the silver ions may react with ions from the exudate leaving few free silver ions for disinfecting.
Another problem with using metals as disinfecting agents in the treatment of open wounds is that metals may be toxic in sufficiently large amounts. If a metal such as silver were to be applied to open wounds, it may enter the bloodstream and end up absorbed by the human body. Once present in the body, silver is not expelled by normal bodily functions and may become imbedded in vital organs such as the liver or the brain.
One dressing uses an inorganic material described in U.S. Pat. No. 5,470,585 to Gilchrist (hereinafter Gilchrist), which consists of a fused mass of sodium and calcium phosphates containing small amounts of silver phosphate. The material is attached to a film dressing and offered as a commercial product called Arglaes(trademark) Controlled Release Island Dressings by Maersk Medical Inc.
The material of the Arglaes(trademark) Controlled Release Dressing releases free silver ions in the presence of an aqueous solution. The material is designed to dissolve completely over a period of several days such that the amount of free silver at any one time is small. When in contact with the aqueous solution, the material dissolves at a rate dependent upon the relative proportions of the readily soluble sodium phosphates and less soluble calcium phosphates present with the release of sodium, calcium, phosphate and silver ions into the solution. The material is impregnated, or mounted on the wound-contacting surface of a polyurethane film. In one example, the material is impregnated in a calcium alginate pad, which is affixed to a polyethylene film.
One problem with the device disclosed in Gilchrist is that the dressing does not maintain the silver ions in the dressing. The silver ions are released into the wound at a rate dependent upon the sodium content and the amount of moisture at the wound site. In addition to potentially being toxic to the patient, the anti-microbial action is sub-optimal. Bacteria are killed at a rate that is dependent on the release of the silver into the wound site, which may not be fast enough. Arglaes(trademark) Controlled Release Island Dressings are described as requiring 2 days to achieve a 99% reduction of bacteria.
It would be desirable to provide a wound dressing that employs silver or other metal ions as a disinfecting agent without releasing the ions into the wound site. It would also be desirable for such a wound dressing to effectively absorb moisture at a wound-site and to be conformable, flexible and easy to apply and remove.
Silver and other disinfecting metals have been used with various compositions as anti-microbial compositions, but few have been applied to a wound dressing.
U.S. Pat. No. 4,525,410 to Hagiwara et al. (hereinafter Hagiwara I) discloses a fiber article having anti-bacterial properties using zeolite particles that retain metal ions. The zeolite is treated with silver nitrate, mixed with various plastic materials, and heat-treated to obtain a fluffy, fibrous article. Hagiwara I does not describe precisely how the fibrous article may be applied, but mentions pillows, mats, beds, bedclothes and insoles of shoes as examples of articles that may apply the article. Hagiwara I does not disclose how or if the fibrous article may be used in medical devices.
Similarly, U.S. Pat. No. 4,775,585 to Hagiwara et al. (hereinafter Hagiwara II) describes polymer articles having antibacterial properties using zeolite. Hagiwara II discloses that such articles may be used as granules, films, fibers, pipes, or other molded articles but lacks any teaching as to the use of such articles in wound treatment.
U.S Pat. No. 5,556,699 to Niira discloses an antibiotic film having at least one organic polymeric film containing antibiotic zeolite. The film disclosed in Niira is less than 15 microns which permits it to maintain transparency. The film is used as a packaging material for packaging foods and medical equipment. No mention is made of its use in wound treatment.
In view of the above, a wound dressing and wound dressing materials are provided that use compositions that incorporate silver and other metals for anti-microbial action. The dressing and dressing materials of the present invention are advantageously highly-absorbent, and protect the wound-site with a high bacteria kill rate. The anti-microbial effect is accomplished using silver or other metal ions maintained in a composition that permits little or no leakage of the metal into the wound-site.
In one aspect of the present invention, a dressing for application on a skin opening is provided having a substantially planar dressing layer. The dressing layer has a skin-contacting surface, and hydrocolloid-adhesive composition mixed with an anti-microbial agent. The anti-microbial agent includes a metallic composition operable to provide disinfecting actions. The hydrocolloid-adhesive composition and anti-microbial agent mixture bind the metallic composition to prevent leakage of the metallic ions into the skin opening.